Collaborative Research: Testing hypotheses of latest Pleistocene paleo-environmental collapse, Northern Channel Islands, California

加州北海峡群岛最新更新世古环境崩溃假说这项研究将描述加州北部海峡群岛(NCI)在最新更新世发生戏剧性古环境变化的性质和时间。特别是，我们将检验主要假设，即岛屿森林砍伐、河流堆积、山体滑坡和大范围燃烧是由火灾制度的急剧变化引起的同步事件--可能与第一批人类的到来和猛犸象的灭绝有关。其他次要假设将得到检验，包括气候逐渐变化造成的变化、气候驱动的火灾频率逐渐增加、海平面上升导致的生态系统减少，或约13ka的撞击事件。最近关于NCI的研究发现，在1300cal yBP左右的关键事件的年龄越来越接近，包括(1)古植物学从针叶树覆盖到非乔木植被的转变，(2)低地沉积的开始，(3)更新世滑坡：(4)木炭和浸染碳的沉积，(5)第一批人类的到来，以及(6)猛犸象在NCI上的灭绝。另一个研究小组提出了大约12.9ka的撞击事件。这项工作将通过以下方面验证这些假设：最新更新世层序的详细地层学描述，OSL和放射性碳测年，孢粉学和古植物学，OIS2后海侵的局部填图，木炭沉积的特征，以及通过最新的更新世-全新世层序对微球和其他潜在的地外标志进行系统采样。火是一种有据可查的机制，通过这种机制，少量的人类可能会对自然系统产生重大影响。作为人类迁入新大陆先锋的区域人为环境影响可能意味着以前没有认识到的时机和规模。

Testing a Hypothesis of Latest Pleistocene Paleo-environmental Collapse, Northern Channel Islands, CaliforniaThis research will describe the nature and timing of dramatic paleo-environmental changes that occurred on the Northern Channel Islands (NCI) of California during the latest Pleistocene. In particular, we will test the primary hypothesis that deforestation of the islands, fluvial aggradations, landsliding, and widespread burning were synchronous events caused by a sharp change in fire regime - per haps associated with the arrival of the first humans and the extinction of mammoths. Other secondary hypotheses will be tested, including changes caused by gradual climate change, gradual climate-driven increases in fire frequency, ecosystem reduction due to sea-level rise, or an impact event at ~13ka. Recent research on the NCI has seen a growing convergence in the ages of key events around 13, 00 cal yBP, including (1) a paleobotanical shift from conifer cover to non-arboreal vegetation, (2) onset of lowland aggradations, (3) Pleistocene landsliding: (4) deposition of charcoal and disseminated carbon; (5) arrival of the first humans, and (6) extinction of mammoths on the NCI. Another research group has suggested an impact event at ~12.9 ka. This work will test these hypotheses through: detailed description of the stratigraphy of latest Pleistocene sequences, OSL and radiocarbon dating, palynology and paleobotany, local mapping of the post-OIS2 transgression, characterization of charcoal deposition, and systematic sampling of microspherules and other potential extraterrestrial indicators through the latest Pleistocene-Holocene sequence. Fire is a documented mechanism by which small numbers of humans may have large impacts on natural systems. Regional anthropogenic environmental impacts at the vanguard of human migration into the New World might imply a timing and magnitude not previously recognized.